95 lines
2.5 KiB
Markdown
95 lines
2.5 KiB
Markdown
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# vcpkg_list
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The latest version of this document lives in the [vcpkg repo](https://github.com/Microsoft/vcpkg/blob/master/docs/maintainers/vcpkg_list.md).
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A replacement for CMake's `list()` function, which correctly handles elements
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with internal semicolons (in other words, escaped semicolons).
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Use `vcpkg_list()` instead of `list()` whenever possible.
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```cmake
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vcpkg_list(SET <out-var> [<element>...])
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vcpkg_list(<COMMAND> <list-var> [<other-arguments>...])
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```
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In addition to all of the commands from `list()`, `vcpkg_list` adds
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a `vcpkg_list(SET)` command.
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This command takes its arguments, escapes them, and then concatenates
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them into a list; this should be used instead of `set()` for setting any
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list variable.
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Otherwise, the `vcpkg_list()` function is the same as the built-in
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`list()` function, with the following restrictions:
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- `GET`, `REMOVE_ITEM`, and `REMOVE_AT` support only one index/value
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- `POP_BACK` and `POP_FRONT` do not support getting the value into
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another out variable. Use C++ style `GET` then `POP_(BACK|FRONT)`.
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- `FILTER` and `TRANSFORM` are unsupported.
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See the [CMake documentation for `list()`](https://cmake.org/cmake/help/latest/command/list.html)
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for more information.
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## Notes: Some Weirdnesses
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The most major weirdness is due to `""` pulling double-duty as "list of zero elements",
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and "list of one element, which is empty". `vcpkg_list` always uses the former understanding.
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This can cause weird behavior, for example:
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```cmake
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set(lst "")
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vcpkg_list(APPEND lst "" "")
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# lst = ";"
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```
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This is because you're appending two elements to the empty list.
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One very weird behavior that comes out of this would be:
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```cmake
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set(lst "")
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vcpkg_list(APPEND lst "")
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# lst = ""
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```
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since `""` is the empty list, we append the empty element and end up with a list
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of one element, which is empty. This does not happen for non-empty lists;
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for example:
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```cmake
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set(lst "a")
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vcpkg_list(APPEND lst "")
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# lst = "a;"
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```
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only the empty list has this odd behavior.
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## Examples
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### Creating a list
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```cmake
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vcpkg_list(SET foo_param)
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if(DEFINED arg_FOO)
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vcpkg_list(SET foo_param FOO "${arg_FOO}")
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endif()
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```
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### Appending to a list
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```cmake
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set(OPTIONS -DFOO=BAR)
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if(VCPKG_TARGET_IS_WINDOWS)
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vcpkg_list(APPEND OPTIONS "-DOS=WINDOWS;FOO")
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endif()
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```
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### Popping the end off a list
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```cmake
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if(NOT list STREQUAL "")
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vcpkg_list(GET list end -1)
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vcpkg_list(POP_BACK list)
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endif()
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```
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## Source
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[scripts/cmake/vcpkg\_list.cmake](https://github.com/Microsoft/vcpkg/blob/master/scripts/cmake/vcpkg_list.cmake)
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